1. Field of the Invention
This invention relates to a pulley unit provided with a one-way clutch. This pulley unit can be installed on an auxiliary machine driven from a crankshaft of an engine of an automobile or the like through a belt. As an auxiliary machine, cited are a compressor for an air conditioner, a water pump, an alternator, a cooling fan and so on of an automobile or the like.
2. Description of the Related Art
Various auxiliary machines installed on an automobile engine are driven through a belt by a crankshaft of the engine. Especially in the case of an alternator among the auxiliary machines, if it is connected in such a manner as to be rotated synchronously with the crankshaft of the engine, when the rotating speed of the crankshaft drops, the power generation capability is lowered.
The applicant of the present invention has considered that the above one-way clutch is built in an alternator, whereby when the rotating speed of a crankshaft drops, the rotation of a rotor of the alternator is continued by its inertia force to heighten the power generation efficiency.
In this case, the one-way clutch is interposed between a pulley of the alternator and the rotor, and according to a rotational difference between the pulley and the rotor, the one-way clutch is switched between the lock state (power transmission state) and the free state (power transmission interruption state) to transmit or cut off power between the pulley and the rotor.
In the described one-way clutch, originally, it is necessary to detent a cage to a member where a cam face is formed for conducting the lock operation and the free operation. As a detent measure for the cage, the applicant of the present invention has considered the construction shown in the specification attached to Japan Utility Model Application No. 5-5162. That is, recessed cam faces formed in several areas of the circumference of an outer ring are extended to one axial end, and projecting parts engaged with the recessed cam faces are provided in the several areas of the circumference of the outer peripheral surface at one axial end of the case, whereby the cage is detented to the outer ring by the circumferential engagement of the projecting parts with the recessed cam faces.
As the conventional one-way clutch is so constructed that the existing recessed cam faces formed on the outer ring are applied to detent the cage, the following disadvantages are caused.
In the first place, the sectional form of the existing recessed cam face does not have a fixed radius of curvature unlike a circular arc. It is considered to be wasteful in respect of cost to work the sectional form of the projecting part corresponding to the recessed cam face with high accuracy only for detent for the cage, so conventionally the projecting part is set to be simply fitted in the recessed cam face. In such a structure, during the lock and free operation of the one-way clutch, the case is liable to be shaken due to the reaction force of an elastic member for energizing a roller, so that the responsiveness at the time of lock and free operation becomes bad and what is worse, there is the possibility that the complete lock state can not be attained. In situations where with the rotating operation of the outer ring body and the inner ring body, vibration is continuously caused, it is pointed out that the cage is sometimes displaced in the axial direction so that the roller is liable to skew and the lock and free operation becomes unstable.
In reflection of the situation as above, there have been proposed the pulley units shown in FIG. 5 through FIG. 8.
The illustrated pulley unit A comprises two, inner and outer ring bodies 1, 2 disposed concentrically, a one-way clutch 3 interposed in an annular space between both ring bodies 1, 2, and two rolling bearings 4, 4 disposed on both sides in the axial direction of the one-way clutch 3 in the annular space.
A groove where a wavy belt B is wrapped is formed on the outer periphery of the outer ring body 1. The outer ring body 1 is driven in rotation through a belt B called V-belt by a crankshaft of an automobile engine or the like. The inner ring body 2 is formed by a sleeve-like member, which is fixed to an input shaft (e.g. a rotor of an alternator) of an auxiliary machine of an automobile, not shown.
The one-way clutch 3 comprises an inner ring 10 having flat key-like cam faces 10a provided in several areas of the circumference of the outer peripheral surface, an outer ring 11 formed to be elongated in the axial direction in such a manner that the rolling bearings 4, 4 are internally fitted to both ends, a cage 12 having a pocket 12a formed to be pierced inside and outside in the radial direction corresponding to the cam face 10a, a plurality of rollers 13 accommodated one by one in each pocket 12a of the cage 12, and coil springs 14 having a substantially rectangular section as an elastic member which are accommodated one by one in each pocket 12a of the cage 12 and adapted to press the roller 13 to the narrow side (lock side) of a wedge space between the cam face 10a and the inner peripheral surface of the outer ring 11. On the inner wall surface of the pocket 12a of the cage 12, as shown in FIG. 6 and FIG. 8, a projection 12b contracted at the root is integrally formed, one axial end of the coil spring 14 is locked and fitted to the contracted part of the root of the projection 12, and the inner periphery of the coil spring 14 is received by the outer periphery of the projection 12 to prevent distortion when the coil spring 14 is compressed. Further, as shown in FIG. 8, a taper surface for facilitating installation of the coil spring 14 is provided on the outside cylindrical surface of the tip of the projection 12b. 
Both of two rolling bearings 4, 4 are formed by a general deep groove ball bearing having an inner ring 16, an outer ring 17, plural balls 18 and a cage 19, and an oil seal 20 as a sealing member is installed only on the axial outer end side between the inner and outer rings 16, 17. That is, the one-way clutch 3 is sealed by two rolling bearings 4, 4, and two rolling bearings 4, 4 and the one-way clutch 3 are lubricated by a common lubricant. Thus, the need of partition construction is eliminated as compared with the case of using the respective lubricants, and also one work operation of injecting a lubricant is sufficient so as to avoid waste.
The operation of the thus constructed pulley unit A will be described. To be short, when the rotating speed of the outer ring body 1 is increased relatively more than that of the inner ring body 2, the roller 13 of the one-way clutch 3 is rolled to the narrow side of the wedge space to be put in the lock state, so that the outer ring body 1 and the inner ring body 2 are integrated and rotated synchronously with each other. However, if the rotating speed of the outer ring body 1 is decreased relatively more than that of the inner ring body 2, the roller 13 of the one-way clutch 3 is rolled to the wide side of the wedge space to be put in the free state, whereby the transmission of rotating power from the outer ring body 1 to the inner ring body 2 is interrupted so that the inner ring body 2 is continuously rotated only by the rotating inertia force.
If the pulley unit A is used in an alternator, regardless of the rotation variation of a crankshaft of an engine as a driving source for a belt B, the rotation of the rotor of the alternator is maintained in a high region to heighten the power generation efficiency. That is, when the rotating speed of the crankshaft is increased, the one-way clutch 3 is put in the lock state to rotate the inner ring body 2 synchronously with the outer ring body 1, and on the contrary, when the rotating speed of the crankshaft is reduced, the one-way clutch 3 is put in the free state so that the inner ring body 2 may be continuously rotated by its rotating inertia force independently of deceleration of the outer ring body 1.
The characteristic construction of the described pulley unit A will now be described. The characteristic construction is mainly that in which the cage 12 of the one-way clutch 3 is immovable in the circumferential direction and in the axial direction. To be concrete, one axial end face of the inner ring 10 of the one-way clutch 3 is provided with a slit-like recessed part 10b which is opened to the shaft end and opened inside and outside in the radial direction, further the inner peripheral side of one axial end of the cage 12 is provided with a projecting part 12c press-fitted in the recessed part 10b from the axial direction, and the circumferential movement of the cage 12 is prohibited by press-fitting of the recessed part 10b and the projecting part 12c. Further, the projecting part 12c is clamped in the axial direction between the inner wall surface of the recessed part 10b and the end face of the inner ring 16 of one rolling bearing 4 disposed on the opening side of the recessed part 10b, thereby prohibiting the axial movement of the cage 12.
The recessed part 10b and the projecting part 12c are provided in two places opposite to each other through 180 degrees in this embodiment. The number may be at least one place or two or more places. If the number is decreased, it is advantageous in that it is not necessary to control the working accuracy not so severely.
If the circumferential and axial movement of the cage 12 of the one-way clutch 3 is thus prohibited, the lock and free operation of the one-way clutch 3 can be conducted stably. That is, If the cage 12 is immovable in the circumferential direction, the reaction force of the resilient energizing force of the roller 13 by the coil spring 14 can be strongly caught, so that the lock operation of the roller 13 can be supported efficiently. On the other hand, if the cage 12 is immovable in the axial direction, even in the situations where vibration and shock are applied from the belt B, the roller 13 is hard to skew. Thus, the lock and free operation of the roller 13 can be stably performed.
Further, since in the proposed embodiment, originally the separation between the recessed part 10b and the projecting part 12c is checked by one rolling bearing 4 provided on the side of the one-way clutch 3, the need of specially using a stop member such as a snap ring or the like can be eliminated to contribute to the reduction in the number of parts and cost.
Further, as the cam face 10a of the one-way clutch 3 is provided on the inner ring 10 in the proposed embodiment, the roller 13 can be prevented from unnecessarily dislocating from the lock position by centrifugal force even in the high speed rotating range. Accordingly, the operational stabilization of the roller 13 can be further heightened by multiplication of the above effect and the effect produced by the movement constraint of the cage 12 so as to contribute to an improvement in reliability.
Though one axial end face of the inner ring 10 of the one-way clutch 3 is provided with a slit-like recessed part 10b extended inside and outside in the radial direction in the proposed embodiment described above, as shown in FIG. 9, the recessed part 10b can be formed like a flat key. In FIG. 9, in order to increased the number of rollers 13 used, the circumferential width of the cam face 10a of the inner ring 10 of the one-way clutch 3 is reduced, and the cam face 10a is a form containing a curve. The part containing a curve is a free rotating position of the roller 13.
Though the coil spring 14 is taken as an example for an elastic member of the one-way clutch 3 in the proposed embodiment described above, it can be replaced by various plate springs and elastic pieces.
Further, though the proposed embodiment described above deals with the case where the cam face 10a of the one-way clutch 3 is formed on the inner ring side, it can be formed on the outer ring side. In the case of the above embodiment, the roller can be prevented from unnecessarily being dislocated from the lock position by centrifugal force even in the high speed rotation range, so it is suitable for use in high speed rotation.
However, the embodiment proposed above is such that the rolling bearings 4, 4 on both sides in the axial direction of the one-way clutch 3 are made into the deep groove ball bearings that have relatively small load bearing capacity. In this connection, it is desired to elevate the load bearing capacity of the belt B to suppress warping of the outer ring body 1 and the inner ring body 2, to make the force skewing the roller 13 of the one-way clutch 3 less easy to be generated, and to further improve stabilization of the locking and free operation of the roller 13.